Filtering medium and processes of producing the same



Patented A r. 14, 1936 UNITED "STATES- PATENT OFFICE 2,037,370 rmrnnme MEDIUM AND raocnssus or PRODUCING THE SAME Gustavus J. Esselen, Swampscott, and William F. Talbot, Auburndale, Mass assignors to Union Wadding Company, Pawtucket, B. L, a come-- ration of Rhode Island No Drawing. Application December 16, 1932,

, Serial No. 647,618

3 Claims.

v The present invention relates to a filtering me-' dium and processes of producing the same.

In the filtration of liquids, for example milk,

speed of filtration is an important consideration in determining the practicability of a filterin'g medium. A medium otherwise'admirably suited cial application. Reduction in the thickness of the filter pad, for example, while expediting the process of filtration without serious loss in emciency of sediment removal, reduces the strength of the filter pad and results in breaking and washing or fiber disarrangement. Increase in the size of the orifices in the filter pad obviously results indecreased' efilciency of sediment re-. moval. Changing the shape of the orifices from essentially round to a narrow slit shape gives good results in the handling of uniform materials where the particles of the sediment to be removed are uniform in size andsymmetrical in shape. But when, as in the filtration of milk, the sediment is neither uniform in size nor symmetrical in shape, the type of filter pad manufactured by combing the fibres essentially into alignment has sacrificed considerable efilciency of sediment retention for the resulting increase in speed of fil tration.-

It is the object of our-invention to provides." method of treating cotton filtering material which will expedite the filtration of liquid, for example milk, therethrough without impairment of theefilciency of sediment removal, and to pro-' duce air-improved cotton-filteringmaterial.

This we accomplish by a chemical treatment of the fibrous cotton with sodium phosphate. The chemicals effective in producing this result are advantageously applied by dissolving the same and treating the fiber with theresulting solution.

We have discovered that proper adjustment ofthe hydrogen ion concentration of such a solu phate solution having a pH between 4 audit.

tion is a very important factor in controlling speed of filtration through the filtering medium thus treated. Good results are obtained'using solutions having a pH between 3 and 'I. We have further found that bestresults are obtained with 5 a solution between pH 4 and pH 6. While we are not certain, it appears that the increase in speed of filtration through cotton media treated in accordance with our invention is probably due to a change produced by the treatment in the cotton itself.

We have found that immersion of the cottonin a sodium phosphate solution materially increases the rate of filtration, without interfering with sediment retention. Among examples of such treatment may be mentioned immersion for one-'half hour in monobasic sodium phosphate solution of pH 4 or immersion in a-solution of dibasic and monobasic sodium phosphates of pH 6.\

It will be noted that in the case of these treat- 9 ments the treating solution isacidie in character.

As stated above, best results are obtained using a solution between pH 4 and pH 6, and itis desirable'to adjust'the pH within these limits by the use of properly buifered solutions.

A typical example of a highly successful treatment is as follows: Washed cotton fiber was immersed for about three minutes in a solution conheavy squeeze rolls, dried and manufactured into filter pads. A 27% increase in speed of filtration. resulted from this treatment.

Having thusdescribed our invention, we claim:- 1. In the treatment of cotton to expedite the filtering of liquid 'therethrough, the step which comprises immersing the cotton in asodium phos- 4o 2. The treatment of cotton to expedite the filtering of milk therethroug'h which comprises immersing fibrouscotton in an aqueous solution of monosodium phosphate and disodium phosphate, removing excess solution'from the fiber-.and dry- 5 ing the fiber; I Y 3. A filtering mediumconsisting of acidic fibrous cotton with sodium phosphate. L 'GUSTAVUS J. ESSELEN. so

WILLIAM F. TALBOT. 

